refactor!: claim references are claim:TAG

lode is renamed paperclaim. A claim reference is claim:TAG or
claim:host/TAG and a pin claim:TAG@hex6 (claimRef and claimPin in
common.schema.json, spec/18 §18.4, spec/02, spec/20); the eight-character
tags do not change. A project names its claim namespace as
claims.paperclaim, and the main example's targeted receipts take the
scope targeted:paperclaim. No old prefix or name is accepted.

paperspec build regenerated the fixtures and vectors: the claim link's and
the symbol's record IDs, the layer receipt, project.json, the two targeted
receipts and Ben's spot-check, the QA report, the inclusion proof, the log's
checkpoint and tiles, and the signature, spot-check, VRF and checkpoint
vectors. The walkthrough and examples quote the new receipt IDs.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SarHTuHhV9cS85XWy2NrLJ

fixtures/README.md

@@ -47,7 +47,7 @@ Each record is a single file, or a folder where a format needs several files.
 | `backend-docling.json`, `backend-examplevendor.json` | The code and weight licenses of a conversion tool and the conditions attached to them. |
 | `profile-acme.json`, `profile-smithlab.json` | What those conditions ask about a team: its purpose, its funding and whom it competes with. |
 | `roster.json` | The keys that may sign, the role of each key's holder in the team, and what each key may sign. Ana is the owner, so she may revoke anyone's receipt. |
-| `layer/` | A layer of annotations on the main example (`layer.json`, `annotations.jsonl`) and the receipt that confirms them (`receipt.json`). Its claim link and its symbol name the claim `amber/k-bond` of lode's example store as lode references it, `lode:272XTX7C`, pinned at `lode:272XTX7C@02f47b`; the symbol names `K_r` by its key, `K_{r}`. |
+| `layer/` | A layer of annotations on the main example (`layer.json`, `annotations.jsonl`) and the receipt that confirms them (`receipt.json`). Its claim link and its symbol name the claim `amber/k-bond` of paperclaim's example store as paperclaim references it, `claim:272XTX7C`, pinned at `claim:272XTX7C@02f47b`; the symbol names `K_r` by its key, `K_{r}`. |
 | `submissions/`, `grades/` | A student's answers to exercises in the layer, and the grader's result for each. |
 | `suspect.json` | A doubtful reading raised for review: the converter's reading of an exponent in the main example, before the first correction answered it. |
 | `qa-report.json` | Reviewer error bounds for a delivery that covers two of the main example's receipts, signed by the team's owner key. |